auto Backward Elim

backwardElimination <- function(x, sl) {
    numVars = length(x)
    for (i in c(1:numVars)){
      regressor = lm(formula = Profit ~ ., data = x)
      maxVar = max(coef(summary(regressor))[c(2:numVars), "Pr(>|t|)"])
      if (maxVar > sl){
        j = which(coef(summary(regressor))[c(2:numVars), "Pr(>|t|)"] == maxVar)
        x = x[, -j]
      }
      numVars = numVars - 1
    }
    return(summary(regressor))
  }

  SL = 0.05
  dataset = dataset[, c(1,2,3,4,5)]
  backwardElimination(training_set, SL)